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1// SPDX-License-Identifier: GPL-2.0
2#include <errno.h>
3#include <sched.h>
4#include "util.h" // for sched_getcpu()
5#include "../perf-sys.h"
6#include "cloexec.h"
7#include "event.h"
8#include "asm/bug.h"
9#include "debug.h"
10#include <unistd.h>
11#include <sys/syscall.h>
12#include <linux/string.h>
13
14static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
15
16int __weak sched_getcpu(void)
17{
18#ifdef __NR_getcpu
19 unsigned cpu;
20 int err = syscall(__NR_getcpu, &cpu, NULL, NULL);
21 if (!err)
22 return cpu;
23#else
24 errno = ENOSYS;
25#endif
26 return -1;
27}
28
29static int perf_flag_probe(void)
30{
31 /* use 'safest' configuration as used in evsel__fallback() */
32 struct perf_event_attr attr = {
33 .type = PERF_TYPE_SOFTWARE,
34 .config = PERF_COUNT_SW_CPU_CLOCK,
35 .exclude_kernel = 1,
36 };
37 int fd;
38 int err;
39 int cpu;
40 pid_t pid = -1;
41 char sbuf[STRERR_BUFSIZE];
42
43 cpu = sched_getcpu();
44 if (cpu < 0)
45 cpu = 0;
46
47 /*
48 * Using -1 for the pid is a workaround to avoid gratuitous jump label
49 * changes.
50 */
51 while (1) {
52 /* check cloexec flag */
53 fd = sys_perf_event_open(&attr, pid, cpu, -1,
54 PERF_FLAG_FD_CLOEXEC);
55 if (fd < 0 && pid == -1 && errno == EACCES) {
56 pid = 0;
57 continue;
58 }
59 break;
60 }
61 err = errno;
62
63 if (fd >= 0) {
64 close(fd);
65 return 1;
66 }
67
68 WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
69 "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
70 err, str_error_r(err, sbuf, sizeof(sbuf)));
71
72 /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
73 while (1) {
74 fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
75 if (fd < 0 && pid == -1 && errno == EACCES) {
76 pid = 0;
77 continue;
78 }
79 break;
80 }
81 err = errno;
82
83 if (fd >= 0)
84 close(fd);
85
86 if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
87 "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
88 err, str_error_r(err, sbuf, sizeof(sbuf))))
89 return -1;
90
91 return 0;
92}
93
94unsigned long perf_event_open_cloexec_flag(void)
95{
96 static bool probed;
97
98 if (!probed) {
99 if (perf_flag_probe() <= 0)
100 flag = 0;
101 probed = true;
102 }
103
104 return flag;
105}
1#include <sched.h>
2#include "util.h"
3#include "../perf.h"
4#include "cloexec.h"
5#include "asm/bug.h"
6#include "debug.h"
7#include <unistd.h>
8#include <asm/unistd.h>
9#include <sys/syscall.h>
10
11static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
12
13int __weak sched_getcpu(void)
14{
15#ifdef __NR_getcpu
16 unsigned cpu;
17 int err = syscall(__NR_getcpu, &cpu, NULL, NULL);
18 if (!err)
19 return cpu;
20#else
21 errno = ENOSYS;
22#endif
23 return -1;
24}
25
26static int perf_flag_probe(void)
27{
28 /* use 'safest' configuration as used in perf_evsel__fallback() */
29 struct perf_event_attr attr = {
30 .type = PERF_TYPE_SOFTWARE,
31 .config = PERF_COUNT_SW_CPU_CLOCK,
32 .exclude_kernel = 1,
33 };
34 int fd;
35 int err;
36 int cpu;
37 pid_t pid = -1;
38 char sbuf[STRERR_BUFSIZE];
39
40 cpu = sched_getcpu();
41 if (cpu < 0)
42 cpu = 0;
43
44 /*
45 * Using -1 for the pid is a workaround to avoid gratuitous jump label
46 * changes.
47 */
48 while (1) {
49 /* check cloexec flag */
50 fd = sys_perf_event_open(&attr, pid, cpu, -1,
51 PERF_FLAG_FD_CLOEXEC);
52 if (fd < 0 && pid == -1 && errno == EACCES) {
53 pid = 0;
54 continue;
55 }
56 break;
57 }
58 err = errno;
59
60 if (fd >= 0) {
61 close(fd);
62 return 1;
63 }
64
65 WARN_ONCE(err != EINVAL && err != EBUSY,
66 "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
67 err, str_error_r(err, sbuf, sizeof(sbuf)));
68
69 /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
70 while (1) {
71 fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
72 if (fd < 0 && pid == -1 && errno == EACCES) {
73 pid = 0;
74 continue;
75 }
76 break;
77 }
78 err = errno;
79
80 if (fd >= 0)
81 close(fd);
82
83 if (WARN_ONCE(fd < 0 && err != EBUSY,
84 "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
85 err, str_error_r(err, sbuf, sizeof(sbuf))))
86 return -1;
87
88 return 0;
89}
90
91unsigned long perf_event_open_cloexec_flag(void)
92{
93 static bool probed;
94
95 if (!probed) {
96 if (perf_flag_probe() <= 0)
97 flag = 0;
98 probed = true;
99 }
100
101 return flag;
102}